1. Field
The present invention relates to a printed circuit board and to a method of manufacturing the printed circuit board.
2. Description of the Related Art
The rigid-flexible printed circuit board is widely being used in mobile electronic products such as cell phones, etc., and in network equipment. The demand for flexibility in the printed circuit board is especially high in mobile electronic products, as they may require operability in fold type or slide type structures or in more complicated structures.
Compared to the board that uses only electrical copper wiring, the board that utilizes optical signals may be less affected by EMI (electromagnetic interference) and EMC (electromagnetic compatibility) and may hence be more resistant to external noise, to thereby allow the transfer of high-speed signals with low loss.
An example of a conventional structure for embedding an optical waveguide in a flexible or a rigid-flexible printed circuit board is illustrated in FIG. 1.
FIG. 1 is a cross sectional view of a printed circuit board according to the related art. In FIG. 1, there are illustrated an optical waveguide 1, a core 2, a cladding 3, insulation films 4, connection pads 5, photoelectric converters 6, a solder resist 7, and solder balls 8.
A printed circuit board according to the related art may include an electrical wiring layer, on which to mount the photoelectric converters, on the upper surface of the optical waveguide 1. This layer structure may be positioned on the uppermost surface of a multilayer board.
Here, a solder resist 7 may be coated over the electrical wiring layer on the uppermost side, with portions corresponding to the pads 5 uncovered to allow connection between the photoelectric converters 6 and the solder balls 8.
This configuration, however, may result in long distances between the photoelectric converters 6 and the optical wiring, and may thus lower the efficiency of the optical connections. Also, when mounting the photoelectric converters 6, it may be necessary to uncover the portions of the solder resist 7 corresponding to the pads 5, as well as the portions between the photoelectric converters and the optical reflector parts. Here, a high level of precision may be required to align the optical wiring and the optical reflector parts.